Biotechnology is one of the fastest growing high-tech fields in the world. As one of the hot spots, antibody drug development continues to improve the health and the life quality of many patients and has achieved remarkable market performance in recent years. Although investments in research and development of new drugs have been increased continuously, the number of innovative drugs that reach the market has dramatically decreased, and many small molecule drugs face the threat of the patent cliff. Therefore, in order to seek new growing points, many pharmaceutical companies are entering the field of antibody drug development. Currently, antibody drugs are widely used in basic biomedical research, diagnosis and treatment of diseases such as cancers, organ transplant rejection and autoimmune diseases.
In recent years, as a large number of therapeutic antibody drugs have been invented and used in the medical field, the production process draws a lot of attention from people. In general, large-scaled economic production of antibody drugs and diagnostic reagents are produced by cell culture at the intracellular level or secreted into the culture medium. The cell culturing process requires a culture medium supplemented with sugars, amino acids, and certain growth factors.
Therefore antibody must be isolated from culture medium as well as other cellular components and purified to a certain level before it can be used as a human therapeutic agent. Currently the most widely used method for antibody purification is affinity chromatography which is simple, fast and highly selective. With those advantages, affinity chromatography significantly reduces the subsequent steps of purification to save time and cost with no sacrifice of purity. Cost control is very important in the modern industrial production processes. If chromatography medium could be used repeatedly, it would significantly reduce the production cost of an antibody. However, previously used chromatography medium may retain un-eluted proteins, protein aggregates, or residual substances that could be harmful, such as viruses or endotoxins. So it is very critical that the previously used media must be cleaned before reusing. The most effective way to clean chromatography medium is Clean-In-Place (CIP) using alkaline solutions. The method involves a treatment with a buffer or solution containing 0.5M Sodium Hydroxide (NaOH). Using this rigorous clean method, impurities can be effectively removed from the medium, however, it may also damage the chromatography medium itself. Therefore, Protein A molecules with high alkali resistance which bind immunoglobulin as described in the present invention can be used as effective ligands for the purification of antibodies. Importantly, the chromatography medium can be treated by CIP with alkali solution and regenerated for repetitive use.